How popular is Anastasiya?

Anastasiya is an unusual first name for women. Anastasiya is an uncommon last name too for both adults and children. (2000 U.S. Census)

Which version is better?

with its source form and related girl names. Popular variation forms of Anastasiya (unlisted) are Anastasia(#216 via latest list) and Anastacia. Other forms, like Anastatia, are uncommon. These relations of Anastasiya were popular as baby names in 2015 (average #1108). Anastasia has generally been popular among parents. (Top 2000 Names, 2015)